Kristin Sullivan woke at 1 a.m. Friday to the sound of dozens of police cars careening past her home on the border of Cambridge and Watertown in Massachusetts. “We are all jumpy after everything that happened at the Boston Marathon,” Sullivan said. “When the first suspect was apprehended, it was only a mile away from our house — right near the local hardware store.”

That suspect was Tamerlan Tsarnaev, who was killed in Watertown after a firefight with police. His brother Dzhokhar, the other main suspect in the bombings, escaped, setting off what Governor Deval Patrick called “a massive manhunt.” In his announcement Friday morning, Patrick said “we are asking people to shelter in place.” Life, for the time being, would have to be lived at home and under siege.

By early Friday morning, the streets of Watertown and Cambridge were deserted, and life in Boston, a major American city, had ground to a standstill. Throughout the day, the media described residents complying with a “lockdown order,” but in reality the governor’s security measure was a request.

“The lockdown is really voluntary, to be honest with you,” says Scott Silliman, emeritus director of the Center on Law, Ethics and National Security at Duke Law School. “The governor said he wants to use sheltering in place. Sheltering in place is a practice normally used if you’re dealing with a pandemic, where you’re telling people, ‘You may have been exposed and we want you to stay exactly where you are so we can isolate everything and we’ll come to you.’”

The “shelter in place” request is legally different from a state of emergency, which Patrick declared earlier this year as winter storm Nemo descended on the Bay State. Patrick imposed a travel ban, threatening a penalty of up to a year in prison and a large fine if people were found on the roads. Massachusetts suffered very few fatalities during the storm.

When it came to keeping the public off the streets on Friday, an order, it seems, wasn’t needed. “When the governor suggested in light of last night’s events that we have an armed subject on the loose who is very dangerous, who has committed murder, I believe the citizens of the commonwealth, in the hopes of helping law enforcement, voluntarily stayed off the streets,” Massachusetts State Trooper Todd Nolan told TIME. “This is a request that the public stay inside and they are adhering to it. There has been no law mentioned or any idea that if you went outside you’d be arrested.”

Legal experts agree that the request has been effective. “If there’s a person running around with explosives in a major population center, it wouldn’t be that surprising that the response of authorities would be to ask people to not be outside,” says David Barron, a professor of public law at Harvard Law School. The heightened risk to the public, given the violence that Dzhokhar Tsarnaev is already alleged to have inflicted, made officials feel the shelter in place request was necessary, but such measures might not be the standard response to every future terrorism manhunt. “If the idea is somehow that the model for how to respond–when there’s any kind of suspect on the loose related to terrorism, they’ll be telling a place to be completely shut down–that seems not at all likely,” Barron says.

Even if Patrick had felt an order was necessary, or if the situation continues, the Massachusetts state constitution empowers Patrick to take steps to ensure the public’s safety. “A state’s chief executive has ample inherent power to prevent carnage,” Harvard Law School professor and constitutional expert Laurence Tribe told TIME in an email. All steps that Patrick has taken so far, Tribe explained, appear to fully comply with the Fourth and Fourteenth Amendments.

The shelter in place order is far from the first time the government has requested the public remain at home for their safety. Silliman points to Toronto’s use of a major quarantine during the 2003 SARS epidemic as one example. Mayors and governors often rely on mandatory evacuations to keep people from harm’s way with impending natural disasters, and curfews are a tool to help contain unrest.

Governments have also resorted to creative methods of keeping law and order in turbulent times. In early April 1968, just after the assassination of Martin Luther King, Jr., Boston officials feared a race riot would engulf the city. City Councilman Tom Atkins had the idea that they could televise a James Brown concert, scheduled for the day after King’s assassination, and keep the city’s youth at home watching the concert on TV. When James balked at performing if the concert was televised and fewer people attended, Boston Mayor Kevin White dipped into the city’s coffers to guarantee Brown’s take of a sold out show.

But orders and creative solutions weren’t necessary in Boston on Friday. As the manhunt continued, people waited anxiously inside their homes. Though Watertown’s residents are no doubt relieved to be safe, some wonder how long Boston can continue in the heightened security state. “My fear is that they don’t find him today,” Jenny Sartori, 43, a professor of Jewish studies at Northeastern University told TIME. “We can’t go on living in lockdown indefinitely. How can you find one person in a whole city?

Swat teams moved block-by-block, knocking on doors and asking people if they had seen anything suspicious. About 11:30 am, a small team of police knocked on the door of James Gillen, a resident of Watertown who lives four blocks from where the shootout happened Thursday. They searched his home and joined up with a larger group, and the 30-officers in their tactical gear, rifles at the ready, patrolled down the street.

As the SWAT officers left Gillen’s home, his two-year-old son asked why they were there. “I had to tell him that the police are looking for a bad guy,” Gillen says. Throughout the long day at home, “he keeps on asking me, ‘Did they get the bad guy?’” The rest of Boston no doubt feels the same way.